lm4871

Embed Size (px)

Citation preview

  • 8/12/2019 lm4871

    1/22

    LM 487 1

    www.ti.com SNAS002E MAY 2004REVISED OCTOBER 2004

    L M 4 8 7 1 3 W A u d io P o w e r A m p lif ie r w ith S h u td o w n M o d eCheck for Samples:LM4871

    1FEATURES DESCRIPTION

    The LM4871 is a mono bridged audio power amplifier2 No Output Coupling Capacitors, Bootstrapcapable of delivering 3W of continuous averageCapacitors, or Snubber Circuits Requiredpower into a 3 load with less than 10% THD when

    Unity-gain Stable powered by a 5V power supply (see Note). To WSON, VSSOP, SOIC, or PDIP Packaging conserve power in portable applications, the

    LM4871's micropower shutdown mode (IQ = 0.6A, External Gain Configuration Capabilitytyp) is activated when VDD is applied to the Pin Compatible with the LM4861 SHUTDOWN pin.

    Boomer audio power amplifiers are designedAPPLICATIONSspecifically to provide high power, high fidelity audio

    Portable Computers output. They require few external components and Desktop Computers operate on low supply voltages from 2.0V to 5.5V.

    Since the LM4871 does not require output coupling Low Voltage Audio Systems

    capacitors, bootstrap capacitors, or snubbernetworks, it is ideally suited for low-power portableKEY SPECIFICATIONSsystems that require minimum volume and weight.

    PO at 10% THD+N, 1kHzAdditional LM4871 features include thermal shutdown

    LM4871LD: 3 , 4 Loads; 3W (typ), protection, unity-gain stability, and external gain set.2.5 W (typ)

    Note: An LM4871LD that has been properly mounted All other LM4871 Packages: 8 load to a circuit board will deliver 3W into 3 (at 10%

    1.5 W (typ) THD). The other package options for the LM4871 will Shutdown Current 0.6A (typ) deliver 1.5W into 8 (at 10% THD). See the

    Application Informationsection for further information Supply Voltage Range 2.0V to 5.5 Vconcerning the LM4871LD, LM4871MM, LM4871M,

    THD at 1kHz at 1W Continuous Average and the LM4871N.Output Power into 8 0.5% (max)

    Connection Diagrams

    Figure 1. VSSOP, Small Outline, and PDIP Figure 2. WSON Package (Top View)Package See Package Number NGN0008ATop View

    See Package Number DGK0008A, D0008A, orD0008E

    1

    Please be aware that an important notice concerning availability, standard warranty, and use in critical applications ofTexas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

    2All trademarks are the property of their respective owners.

    PRODUCTION DATA information is current as of publication date. Copyright 2004, Texas Instruments IncorporatedProducts conform to specifications per the terms of the TexasInstruments standard warranty. Production processing does not

    necessarily include testing of all parameters.

    http://www.ti.com/product/lm4871?qgpn=lm4871http://www.ti.com/http://www.ti.com/product/lm4871#sampleshttp://www.ti.com/product/lm4871#sampleshttp://www.ti.com/http://www.ti.com/product/lm4871?qgpn=lm4871
  • 8/12/2019 lm4871

    2/22

    LM 487 1

    SNAS002E MAY 2004 REVISED OCTOBER 2004 www.ti.com

    Typical Application

    Figure 3. Typical Audio Amplifier Application Circuit

    These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foamduring storage or handling to prevent electrostatic damage to the MOS gates.

    2 Submit Documentation Feedback Copyright 2004, Texas Instruments Incorporated

    Product Folder Links:LM4871

    http://www.ti.com/product/lm4871?qgpn=lm4871http://www.ti.com/http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=SNAS002E&partnum=LM4871http://www.ti.com/product/lm4871?qgpn=lm4871http://www.ti.com/product/lm4871?qgpn=lm4871http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=SNAS002E&partnum=LM4871http://www.ti.com/http://www.ti.com/product/lm4871?qgpn=lm4871
  • 8/12/2019 lm4871

    3/22

    LM 487 1

    www.ti.com SNAS002E MAY 2004REVISED OCTOBER 2004

    Absolute Maximum Ratings (1)(2)

    Supply Voltage 6.0V

    Supply Temperature 65C to +150C

    Input Voltage 0.3V to VDD to +0.3V

    Power Dissipation (3) Internally Limited

    ESD Susceptibility (4) 5000V

    ESD Susceptibility (5) 250V

    Junction Temperature 150C

    Soldering Information Small Outline Package Vapor Phase (60 sec.) 215C

    Infrared (15 sec.) 220C

    JC(typ)D0008A 35C/W

    JA(typ)D0008A 140C/W

    JC(typ)D0008E 37C/W

    JA(typ)D0008E 107C/W

    JC(typ)DGK0008A 56C/W

    JA(typ)DGK0008A 210C/W

    JC(typ)NGN0008A 4.3C/W

    JA(typ)NGN0008A 56C/W(6)

    (1) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions forwhich the device is functional, but do not ensure specific performance limits. Electrical Characteristics state DC and AC electricalspecifications under particular test conditions which ensure specific performance limits. This assumes that the device is within theOperating Ratings. Specifications are not ensured for parameters where no limit is given, however, the typical value is a good indicationof device performance.

    (2) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability andspecifications.

    (3) The maximum power dissipation must be derated at elevated temperatures and is dictated by TJMAX, JA, and the ambient temperatureTA. The maximum allowable power dissipation is P DMAX= (TJMAXTA)/JAor the number given in Absolute Maximum Ratings, whicheveris lower. For the LM4871, TJMAX= 150C. For the JA's for different packages, please see the Application Informationsection or theabsolute maximum ratings section.

    (4) Human body model, 100pF discharged through a 1.5k resistor.(5) Machine Model, 220pF240pF discharged through all pins.(6) The given JA is for an LM4871 packaged in an NGN0008A with the ExposedDAP soldered to an exposed 1in

    2 area of 1oz printedcircuit board copper.

    Operating RatingsTemperature Range TMIN TA TMAX 40C TA 85C

    Supply Voltage 2.0V VDD 5.5V

    Electrical Characteristics(1)(2)

    The following specifications apply for VDD= 5V and RL= 8unless otherwise specified. Limits apply for TA= 25C.

    LM4871

    Symbol Parameter Conditions UnitsMin (3) Typical (4) Limit(3)

    (Limits)

    VDD Supply Voltage 2.0 5.5 V

    IDD Quiescent Power Supply VIN = 0V, Io= 0A 6.5 10.0 mA

    CurrentISD Shutdown Current VPIN1= VDD 0.6 2 A

    VOS Output Offset Voltage VIN = 0V 5.0 50 mV

    (1) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions forwhich the device is functional, but do not ensure specific performance limits. Electrical Characteristics state DC and AC electricalspecifications under particular test conditions which ensure specific performance limits. This assumes that the device is within theOperating Ratings. Specifications are not ensured for parameters where no limit is given, however, the typical value is a good indicationof device performance.

    (2) All voltages are measured with respect to the ground pin, unless otherwise specified.(3) Typicals are specified at 25C and represent the parametric norm.(4) Limits are specified to TI's AOQL (Average Outgoing Quality Level).

    Copyright 2004, Texas Instruments Incorporated Submit Documentation Feedback 3

    Product Folder Links:LM4871

    http://www.ti.com/product/lm4871?qgpn=lm4871http://www.ti.com/http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=SNAS002E&partnum=LM4871http://www.ti.com/product/lm4871?qgpn=lm4871http://www.ti.com/product/lm4871?qgpn=lm4871http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=SNAS002E&partnum=LM4871http://www.ti.com/http://www.ti.com/product/lm4871?qgpn=lm4871
  • 8/12/2019 lm4871

    4/22

    LM 487 1

    SNAS002E MAY 2004 REVISED OCTOBER 2004 www.ti.com

    Electrical Characteristics(1)(2) (continued)

    The following specifications apply for VDD= 5V and RL= 8unless otherwise specified. Limits apply for TA= 25C.

    LM4871

    Symbol Parameter Conditions UnitsMin (3) Typical (4) Limit(3)

    (Limits)

    Po Output Power THD = 1%, f = 1kHz

    LM4871LD, RL= 3 (5) 2.38 WLM4871LD, RL= 4

    (5) 2LM4871, RL= 8

    (5) 1.2

    THD+N = 10%, f = 1kHzLM4871LD, RL= 3

    (5) 3W

    LM4871LD, RL= 4(5) 2.5

    LM4871, RL= 8(5) 1.5

    THD+N Total Harmonic 20Hz f 20kHz, AVD= 2Distortion+Noise LM4871LD, RL= 4, P O = 1.6W 0.13 %

    LM4871, RL= 8, P O = 1W 0.25

    PSRR Power Supply Rejection Ratio VDD= 4.9V to 5.1V 60 dB

    (5) When driving 3 or 4 loads from a 5V supply, the LM4871LD must be mounted to a circuit board.

    External Components Description(Figure 3)

    Components Functional Description

    1. Ri Inverting input resistance that sets the closed-loop gain in conjunction with Rf. This resistor also forms a high pass filterwith Ciat fC= 1/(2RiCi).

    2. Ci Input coupling capacitor that blocks the DC voltage at the amplifiers input terminals. Also creates a highpass filter withRiat fc= 1/(2RiCi). Refer to the section,Proper Selection of External Components, for an explanation of how todetermine the value of Ci.

    3. Rf Feedback resistance that sets the closed-loop gain in conjunction with Ri.

    4. CS Supply bypass capacitor that provides power supply filtering. Refer to thePower Supply Bypassingsection forinformation concerning proper placement and selection of the supply bypass capacitor.

    5. CB Bypass pin capacitor that provides half-supply filtering. Refer to the section,Proper Selection of External Components,for information concerning proper placement and selection of C B.

    4 Submit Documentation Feedback Copyright 2004, Texas Instruments Incorporated

    Product Folder Links:LM4871

    http://www.ti.com/product/lm4871?qgpn=lm4871http://www.ti.com/http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=SNAS002E&partnum=LM4871http://www.ti.com/product/lm4871?qgpn=lm4871http://www.ti.com/product/lm4871?qgpn=lm4871http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=SNAS002E&partnum=LM4871http://www.ti.com/http://www.ti.com/product/lm4871?qgpn=lm4871
  • 8/12/2019 lm4871

    5/22

    LM 487 1

    www.ti.com SNAS002E MAY 2004REVISED OCTOBER 2004

    Typical Performance CharacteristicsNGN Specific Characteristics

    LM4871LD THD+N vs Output Power LM4871LD THD+N vs Frequency

    Figure 4. Figure 5.

    LM4871LD THD+N vs Frequency LM4871LD THD+N vs Output Power

    Figure 6. Figure 7.

    LM4871LD Power Dissipation vs Output Power LM4871LD Power Derating Curve

    This curve shows the LM4871LD's thermal dissipation ability at

    different ambient temperatures given the exposed-DAP of the part is

    soldered to a plane of 1oz. Cu with an area given in the label of each

    curve. This label also designates whether the plane exists on the

    same (top) layer as the chip, on the bottom layer, or on both layers.

    Infinite heatsink and unattached (no heatsink) conditions are also

    shown.Figure 8. Figure 9.

    Copyright 2004, Texas Instruments Incorporated Submit Documentation Feedback 5

    Product Folder Links:LM4871

    http://www.ti.com/product/lm4871?qgpn=lm4871http://www.ti.com/http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=SNAS002E&partnum=LM4871http://www.ti.com/product/lm4871?qgpn=lm4871http://www.ti.com/product/lm4871?qgpn=lm4871http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=SNAS002E&partnum=LM4871http://www.ti.com/http://www.ti.com/product/lm4871?qgpn=lm4871
  • 8/12/2019 lm4871

    6/22

    LM 487 1

    SNAS002E MAY 2004 REVISED OCTOBER 2004 www.ti.com

    Typical Performance CharacteristicsNon-NGN Specific Characteristics

    THD+N vs Frequency THD+N vs Frequency

    Figure 10. Figure 11.

    THD+N vs Frequency THD+N vs Output Power

    Figure 12. Figure 13.

    THD+N vs Output Power THD+N vs Output Power

    Figure 14. Figure 15.

    6 Submit Documentation Feedback Copyright 2004, Texas Instruments Incorporated

    Product Folder Links:LM4871

    http://www.ti.com/product/lm4871?qgpn=lm4871http://www.ti.com/http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=SNAS002E&partnum=LM4871http://www.ti.com/product/lm4871?qgpn=lm4871http://www.ti.com/product/lm4871?qgpn=lm4871http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=SNAS002E&partnum=LM4871http://www.ti.com/http://www.ti.com/product/lm4871?qgpn=lm4871
  • 8/12/2019 lm4871

    7/22

    LM 487 1

    www.ti.com SNAS002E MAY 2004REVISED OCTOBER 2004

    Typical Performance Characteristics

    Non-NGN Specific Characteristics (continued)Output Power vs Supply Voltage Output Power vs Supply Voltage

    Figure 16. Figure 17.

    Output Power vs Supply Voltage Output Power vs Load Resistance

    Figure 18. Figure 19.

    Power Dissipation vs Output Power Power Derating Curve

    Figure 20. Figure 21.

    Copyright 2004, Texas Instruments Incorporated Submit Documentation Feedback 7

    Product Folder Links:LM4871

    http://www.ti.com/product/lm4871?qgpn=lm4871http://www.ti.com/http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=SNAS002E&partnum=LM4871http://www.ti.com/product/lm4871?qgpn=lm4871http://www.ti.com/product/lm4871?qgpn=lm4871http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=SNAS002E&partnum=LM4871http://www.ti.com/http://www.ti.com/product/lm4871?qgpn=lm4871
  • 8/12/2019 lm4871

    8/22

    LM 487 1

    SNAS002E MAY 2004 REVISED OCTOBER 2004 www.ti.com

    Typical Performance Characteristics

    Non-NGN Specific Characteristics (continued)Clipping Voltage vs Supply Voltage Noise Floor

    Figure 22. Figure 23.

    Frequency Response vs Input Capacitor Size Power Supply Rejection Ratio

    Figure 24. Figure 25.

    Open Loop Frequency Response Supply Current vs Supply Voltage

    Figure 26. Figure 27.

    8 Submit Documentation Feedback Copyright 2004, Texas Instruments Incorporated

    Product Folder Links:LM4871

    http://www.ti.com/product/lm4871?qgpn=lm4871http://www.ti.com/http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=SNAS002E&partnum=LM4871http://www.ti.com/product/lm4871?qgpn=lm4871http://www.ti.com/product/lm4871?qgpn=lm4871http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=SNAS002E&partnum=LM4871http://www.ti.com/http://www.ti.com/product/lm4871?qgpn=lm4871
  • 8/12/2019 lm4871

    9/22

    LM 487 1

    www.ti.com SNAS002E MAY 2004REVISED OCTOBER 2004

    APPLICATION INFORMATION

    EXPOSED-DAP PACKAGE PCB MOUNTING CONSIDERATION

    The LM4871's exposed-DAP (die attach paddle) package (NGN) provides a low thermal resistance between thedie and the PCB to which the part is mounted and soldered. This allows rapid heat transfer from the die to thesurrounding PCB copper traces, ground plane, and surrounding air. The result is a low voltage audio power

    amplifier that produces 2W at 1% THD with a 4 load. This high power is achieved through carefulconsideration of necessary thermal design. Failing to optimize thermal design may compromise the LM4871'shigh power performance and activate unwanted, though necessary, thermal shutdown protection.

    The NGN package must have its DAP soldered to a copper pad on the PCB. The DAP's PCB copper pad isconnected to a large plane of continuous unbroken copper. This plane forms a thermal mass, heat sink, andradiation area. Place the heat sink area on either outside plane in the case of a two-sided PCB, or on an innerlayer of a board with more than two layers. Connect the DAP copper pad to the inner layer or backside copperheat sink area with 4(2x2) vias. The via diameter should be 0.012in-0.013in with a 1.27mm pitch. Ensure efficientthermal conductivity by plating through the vias.

    Best thermal performance is achieved with the largest practical heat sink area. If the heatsink and amplifier sharethe same PCB layer, a nominal 2.5in2 area is necessary for 5V operation with a 4 load. Heatsink areas notplaced on the same PCB layer as the LM4871 should be 5in2 (min) for the same supply voltage and loadresistance. The last two area recommendations apply for 25C ambient temperature. Increase the area to

    compensate for ambient temperatures above 25C. The LM4871's power de-rating curve in the TypicalPerformance Characteristicsshows the maximum power dissipation versus temperature. An example PCB layoutfor the NGN package is shown in the Demonstration Board Layout section. Further detailed and specificinformation concerning PCB layout, fabrication, and mounting an NGN (WSON) package is available from TI'sPackage Engineering Group under application note AN1187.

    PCB LAYOUT AND SUPPLY REGULATION CONSIDERATIONS FOR DRIVING 3 AND 4LOADS

    Power dissipated by a load is a function of the voltage swing across the load and the load's impedance. As loadimpedance decreases, load dissipation becomes increasingly dependant on the interconnect (PCB trace andwire) resistance between the amplifier output pins and the load's connections. Residual trace resistance causesa voltage drop, which results in power dissipated in the trace and not in the load as desired. For example, 0.1trace resistance reduces the output power dissipated by a 4 load from 2.0W to 1.95W. This problem of

    decreased load dissipation is exacerbated as load impedance decreases. Therefore, to maintain the highest loaddissipation and widest output voltage swing, PCB traces that connect the output pins to a load must be as wideas possible.

    Poor power supply regulation adversely affects maximum output power. A poorly regulated supply's outputvoltage decreases with increasing load current. Reduced supply voltage causes decreased headroom, outputsignal clipping, and reduced output power. Even with tightly regulated supplies, trace resistance creates thesame effects as poor supply regulation. Therefore, making the power supply traces as wide as possible helpsmaintain full output voltage swing.

    BRIDGE CONFIGURATION EXPLANATION

    As shown inFigure 3, the LM4871 has two operational amplifiers internally, allowing for a few different amplifierconfigurations. The first amplifier's gain is externally configurable; the second amplifier is internally fixed in aunity-gain, inverting configuration. The closed-loop gain of the first amplifier is set by selecting the ratio of R f to Riwhile the second amplifier's gain is fixed by the two internal 40k resistors. Figure 3 shows that the output ofamplifier one serves as the input to amplifier two, which results in both amplifiers producing signals identical inmagnitude, but 180out of phase. Consequently, the differential gain for the IC is

    AVD= 2 *(Rf/Ri) (1)

    By driving the load differentially through outputs Vo1 and Vo2, an amplifier configuration commonly referred to asbridged mode is established. Bridged mode operation is different from the classical single-ended amplifierconfiguration where one side of its load is connected to ground.

    Copyright 2004, Texas Instruments Incorporated Submit Documentation Feedback 9

    Product Folder Links:LM4871

    http://www.ti.com/product/lm4871?qgpn=lm4871http://www.ti.com/http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=SNAS002E&partnum=LM4871http://www.ti.com/product/lm4871?qgpn=lm4871http://www.ti.com/product/lm4871?qgpn=lm4871http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=SNAS002E&partnum=LM4871http://www.ti.com/http://www.ti.com/product/lm4871?qgpn=lm4871
  • 8/12/2019 lm4871

    10/22

  • 8/12/2019 lm4871

    11/22

    LM 487 1

    www.ti.com SNAS002E MAY 2004REVISED OCTOBER 2004

    SHUTDOWN FUNCTION

    In order to reduce power consumption while not in use, the LM4871 contains a shutdown pin to externally turn offthe amplifier's bias circuitry. This shutdown feature turns the amplifier off when a logic high is placed on theshutdown pin. The trigger point between a logic low and logic high level is typically half- supply. It is best toswitch between ground and supply to provide maximum device performance. By switching the shutdown pin toVDD, the LM4871 supply current draw will be minimized in idle mode. While the device will be disabled with

    shutdown pin voltages less then VDD, the idle current may be greater than the typical value of 0.6A. In eithercase, the shutdown pin should be tied to a definite voltage to avoid unwanted state changes.

    In many applications, a microcontroller or microprocessor output is used to control the shutdown circuitry whichprovides a quick, smooth transition into shutdown. Another solution is to use a single-pole, single-throw switch inconjunction with an external pull-up resistor. When the switch is closed, the shutdown pin is connected to groundand enables the amplifier. If the switch is open, then the external pull-up resistor will disable the LM4871. Thisscheme ensures that the shutdown pin will not float thus preventing unwanted state changes.

    PROPER SELECTION OF EXTERNAL COMPONENTS

    Proper selection of external components in applications using integrated power amplifiers is critical to optimizedevice and system performance. While the LM4871 is tolerant of external component combinations,consideration to component values must be used to maximize overall system quality.

    The LM4871 is unity-gain stable which gives a designer maximum system flexibility. The LM4871 should be usedin low gain configurations to minimize THD+N values, and maximize the signal to noise ratio. Low gainconfigurations require large input signals to obtain a given output power. Input signals equal to or greater than 1Vrms are available from sources such as audio codecs. Please refer to the section, Audio Power AmplifierDesign, for a more complete explanation of proper gain selection.

    Besides gain, one of the major considerations is the closed-loop bandwidth of the amplifier. To a large extent, thebandwidth is dictated by the choice of external components shown in Audio Power Amplifier Design. The inputcoupling capacitor, Ci, forms a first order high pass filter which limits low frequency response. This value shouldbe chosen based on needed frequency response for a few distinct reasons.

    Selection Of Input Capacitor Size

    Large input capacitors are both expensive and space hungry for portable designs. Clearly, a certain sizedcapacitor is needed to couple in low frequencies without severe attenuation. But in many cases the speakers

    used in portable systems, whether internal or external, have little ability to reproduce signals below 100Hz to150Hz. Thus, using a large input capacitor may not increase actual system performance.

    In addition to system cost and size, click and pop performance is effected by the size of the input couplingcapacitor, Ci. A larger input coupling capacitor requires more charge to reach its quiescent DC voltage (nominally1/2 VDD). This charge comes from the output via the feedback and is apt to create pops upon device enable.Thus, by minimizing the capacitor size based on necessary low frequency response, turn-on pops can beminimized.

    Besides minimizing the input capacitor size, careful consideration should be paid to the bypass capacitor value.Bypass capacitor, CB, is the most critical component to minimize turn-on pops since it determines how fast theLM4871 turns on. The slower the LM4871's outputs ramp to their quiescent DC voltage (nominally 1/2 V DD), thesmaller the turn-on pop. Choosing CB equal to 1.0F along with a small value of C i (in the range of 0.1F to0.39F), should produce a virtually clickless and popless shutdown function. While the device will functionproperly, (no oscillations or motorboating), with CB equal to 0.1F, the device will be much more susceptible to

    turn-on clicks and pops. Thus, a value of CB equal to 1.0F is recommended in all but the most cost sensitivedesigns.

    Copyright 2004, Texas Instruments Incorporated Submit Documentation Feedback 11

    Product Folder Links:LM4871

    http://www.ti.com/product/lm4871?qgpn=lm4871http://www.ti.com/http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=SNAS002E&partnum=LM4871http://www.ti.com/product/lm4871?qgpn=lm4871http://www.ti.com/product/lm4871?qgpn=lm4871http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=SNAS002E&partnum=LM4871http://www.ti.com/http://www.ti.com/product/lm4871?qgpn=lm4871
  • 8/12/2019 lm4871

    12/22

    LM 487 1

    SNAS002E MAY 2004 REVISED OCTOBER 2004 www.ti.com

    AUDIO POWER AMPLIFIER DESIGN

    Design a 1W/8 Audio Amplifier

    Given:

    Power Output 1 Wrms

    Load Impedance 8

    Input Level 1 Vrms

    Input Impedance 20 k

    Bandwidth 100 Hz20 kHz 0.25 dB

    A designer must first determine the minimum supply rail to obtain the specified output power. By extrapolatingfrom the Output Power vs Supply Voltage graphs in the Typical Performance Characteristicssection, the supplyrail can be easily found. A second way to determine the minimum supply rail is to calculate the required VopeakusingEquation 4and add the output voltage. Using this method, the minimum supply voltage would be (V opeak+(VODTOP+ VODBOT)), where VODBOTand VODTOPare extrapolated from the Dropout Voltage vs Supply Voltage curve intheTypical Performance Characteristicssection.

    (4)

    Using the Output Power vs Supply Voltage graph for an 8 load, the minimum supply rail is 4.6V. But since 5V isa standard voltage in most applications, it is chosen for the supply rail. Extra supply voltage creates headroomthat allows the LM4871 to reproduce peaks in excess of 1W without producing audible distortion. At this time, thedesigner must make sure that the power supply choice along with the output impedance does not violate theconditions explained in thePOWER DISSIPATIONsection.

    Once the power dissipation equations have been addressed, the required differential gain can be determinedfromEquation 5.

    (5)

    Rf/Ri= AVD/2 (6)

    FromEquation 5, the minimum AVDis 2.83; use AVD= 3.

    Since the desired input impedance was 20k, and with a AVD impedance of 2, a ratio of 1.5:1 of R f to Ri resultsin an allocation of Ri = 20k and Rf = 30k. The final design step is to address the bandwidth requirementswhich must be stated as a pair of 3dB frequency points. Five times away from a 3dB point is 0.17dB downfrom passband response which is better than the required 0.25dB specified.

    fL= 100Hz/5 = 20Hz

    fH= 20kHz * 5 = 100kHz

    As stated in theExternal Components Descriptionsection, Riin conjunction with Cicreate a highpass filter.

    Ci 1/(2*20k*20Hz) = 0.397F; use 0.39F

    The high frequency pole is determined by the product of the desired frequency pole, f H, and the differential gain,AVD. With a AVD = 3 and fH = 100kHz, the resulting GBWP = 150kHz which is much smaller than the LM4871GBWP of 4MHz. This figure displays that if a designer has a need to design an amplifier with a higher differential

    gain, the LM4871 can still be used without running into bandwidth limitations.

    12 Submit Documentation Feedback Copyright 2004, Texas Instruments Incorporated

    Product Folder Links:LM4871

    http://www.ti.com/product/lm4871?qgpn=lm4871http://www.ti.com/http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=SNAS002E&partnum=LM4871http://www.ti.com/product/lm4871?qgpn=lm4871http://www.ti.com/product/lm4871?qgpn=lm4871http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=SNAS002E&partnum=LM4871http://www.ti.com/http://www.ti.com/product/lm4871?qgpn=lm4871
  • 8/12/2019 lm4871

    13/22

    LM 487 1

    www.ti.com SNAS002E MAY 2004REVISED OCTOBER 2004

    Demonstration Board Layout

    Figure 28. Recommended NGN PC Board Layout: Figure 29. Recommended NGN PC Board Layout:Component-Side Silkscreen Component-Side Layout

    Figure 30. Recommended NGN PC Board Layout: Bottom-Side Layout

    LM4871 MDA MWA 3W Audio Power Amplifier With Shutdown Mode

    Figure 31. Die Layout (C - Step)

    Copyright 2004, Texas Instruments Incorporated Submit Documentation Feedback 13

    Product Folder Links:LM4871

    http://www.ti.com/product/lm4871?qgpn=lm4871http://www.ti.com/http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=SNAS002E&partnum=LM4871http://www.ti.com/product/lm4871?qgpn=lm4871http://www.ti.com/product/lm4871?qgpn=lm4871http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=SNAS002E&partnum=LM4871http://www.ti.com/http://www.ti.com/product/lm4871?qgpn=lm4871
  • 8/12/2019 lm4871

    14/22

    LM 487 1

    SNAS002E MAY 2004 REVISED OCTOBER 2004 www.ti.com

    Die/Wafer Characteristics

    Fabrication Attributes General Die Information

    Physical Die Identification LM4871C Bond Pad Opening Size (min) 102m x 102m

    Die Step C Bond Pad Metalization 0.5% COPPER_BAL.ALUMINUM

    Physical Attributes Passivation NITRIDEWafer Diameter 150mm Back Side Metal BARE BACK

    Dise Size (Drawn) 1372m x 1758m Back Side Connection GND54mils x 69mils

    Thickness 406m Nominal

    Min Pitch 164m Nominal

    Special Assembly Requirements:

    Note: Actual die size is rounded to the nearest micron.

    Die Bond Pad Coordinate Locations (C - Step)

    (Referenced to die center, coordinates in m) NC = No Connection

    X/Y COORDINATES PAD SIZESIGNAL NAME PAD# NUMBERX Y X Y

    SHUTDOWN 1 -559 541 102 x 102

    BYPASS 2 -559 376 102 x 102

    NC 3 -559 -45 102 x 210

    INPUT + 4 -559 -248 102 x 102

    INPUT - 5 -559 -486 102 x 102

    GND 6 -476 -725 102 x 102

    VOUT 1 7 -135 -598 102 x 210

    GND 8 554 -686 102 x 102

    VDD 9 554 -4 102 x 210

    GND 10 554 568 102 x 102

    VOUT 2 11 -135 598 102 x 210

    GND 12 -473 752 102 x 102

    14 Submit Documentation Feedback Copyright 2004, Texas Instruments Incorporated

    Product Folder Links:LM4871

    http://www.ti.com/product/lm4871?qgpn=lm4871http://www.ti.com/http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=SNAS002E&partnum=LM4871http://www.ti.com/product/lm4871?qgpn=lm4871http://www.ti.com/product/lm4871?qgpn=lm4871http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=SNAS002E&partnum=LM4871http://www.ti.com/http://www.ti.com/product/lm4871?qgpn=lm4871
  • 8/12/2019 lm4871

    15/22

    PACKAGE OPTION ADDENDUM

    www.ti.com 9-Mar-2013

    Addendum-Page 1

    PACKAGING INFORMATION

    Orderable Device Status

    (1)

    Package Type PackageDrawing

    Pins Package Qty Eco Plan

    (2)

    Lead/Ball Finish MSL Peak Temp

    (3)

    Op Temp (C) Top-Side Markings

    (4)

    Samples

    LM4871LD ACTIVE WSON NGN 8 1000 TBD Call TI Call TI -40 to 85 L4871

    LM4871LD/NOPB ACTIVE WSON NGN 8 1000 Green (RoHS

    & no Sb/Br)

    SN Level-3-260C-168 HR -40 to 85 L4871

    LM4871LDX/NOPB ACTIVE WSON NGN 8 4500 Green (RoHS

    & no Sb/Br)

    SN Level-3-260C-168 HR -40 to 85 L4871

    LM4871M ACTIVE SOIC D 8 95 TBD Call TI Call TI -40 to 85 4871

    LM4871M/NOPB ACTIVE SOIC D 8 95 Green (RoHS

    & no Sb/Br)

    CU SN Level-1-260C-UNLIM -40 to 85 4871

    LM4871MM ACTIVE VSSOP DGK 8 1000 TBD Call TI Call TI -40 to 85 G71

    LM4871MM/NOPB ACTIVE VSSOP DGK 8 1000 Green (RoHS

    & no Sb/Br)

    CU SN Level-1-260C-UNLIM -40 to 85 G71

    LM4871MMX/NOPB ACTIVE VSSOP DGK 8 3500 Green (RoHS

    & no Sb/Br)

    CU SN Level-1-260C-UNLIM -40 to 85 G71

    LM4871MX ACTIVE SOIC D 8 2500 TBD Call TI Call TI -40 to 85 4871

    LM4871MX/NOPB ACTIVE SOIC D 8 2500 Green (RoHS

    & no Sb/Br)

    CU SN Level-1-260C-UNLIM -40 to 85 4871

    (1)

    The marketing status values are defined as follows:ACTIVE:Product device recommended for new designs.LIFEBUY:TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.NRND:Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.

    PREVIEW:Device has been announced but is not in production. Samples may or may not be available.OBSOLETE:TI has discontinued the production of the device.

    (2)

    Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontentfor the latest availabilityinformation and additional product content details.TBD: The Pb-Free/Green conversion plan has not been defined.Pb-Free (RoHS):TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement thatlead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.Pb-Free (RoHS Exempt):This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used betweenthe die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.Green (RoHS & no Sb/Br):TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weightin homogeneous material)

    http://www.ti.com/productcontenthttp://www.ti.com/product/LM4871?CMP=conv-poasamples#samplebuyhttp://www.ti.com/product/LM4871?CMP=conv-poasamples#samplebuyhttp://www.ti.com/product/LM4871?CMP=conv-poasamples#samplebuyhttp://www.ti.com/product/LM4871?CMP=conv-poasamples#samplebuyhttp://www.ti.com/product/LM4871?CMP=conv-poasamples#samplebuyhttp://www.ti.com/product/LM4871?CMP=conv-poasamples#samplebuyhttp://www.ti.com/product/LM4871?CMP=conv-poasamples#samplebuyhttp://www.ti.com/product/LM4871?CMP=conv-poasamples#samplebuyhttp://www.ti.com/product/LM4871?CMP=conv-poasamples#samplebuyhttp://www.ti.com/product/LM4871?CMP=conv-poasamples#samplebuy
  • 8/12/2019 lm4871

    16/22

    PACKAGE OPTION ADDENDUM

    www.ti.com 9-Mar-2013

    Addendum-Page 2

    (3)MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.

    (4)

    Only one of markings shown within the brackets will appear on the physical device.

    Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on informationprovided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken andcontinues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.

    In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.

  • 8/12/2019 lm4871

    17/22

  • 8/12/2019 lm4871

    18/22

    *All dimensions are nominal

    Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)

    LM4871LD WSON NGN 8 1000 203.0 190.0 41.0

    LM4871LD/NOPB WSON NGN 8 1000 203.0 190.0 41.0

    LM4871LDX/NOPB WSON NGN 8 4500 358.0 343.0 63.0

    LM4871MM VSSOP DGK 8 1000 203.0 190.0 41.0

    LM4871MM/NOPB VSSOP DGK 8 1000 203.0 190.0 41.0

    LM4871MMX/NOPB VSSOP DGK 8 3500 349.0 337.0 45.0

    LM4871MX SOIC D 8 2500 349.0 337.0 45.0

    LM4871MX/NOPB SOIC D 8 2500 349.0 337.0 45.0

    PACKAGE MATERIALS INFORMATION

    www.ti.com 26-Jan-2013

    Pack Materials-Page 2

  • 8/12/2019 lm4871

    19/22

  • 8/12/2019 lm4871

    20/22

    MECHANICAL DATA

    NGN0008A

    www.ti.com

    LDC08A (Rev B)

  • 8/12/2019 lm4871

    21/22

  • 8/12/2019 lm4871

    22/22

    IMPORTANT NOTICE

    Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and otherchanges to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latestissue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current andcomplete. All semiconductor products (also referred to herein as components) are sold subject to TIs terms and conditions of salesupplied at the time of order acknowledgment.

    TI warrants performance of its components to the specifications applicable at the time of sale, in accordance with the warranty in TIs terms

    and conditions of sale of semiconductor products. Testing and other quality control techniques are used to the extent TI deems necessaryto support this warranty. Except where mandated by applicable law, testing of all parameters of each component is not necessarilyperformed.

    TI assumes no liability for applications assistance or the design of Buyers products. Buyers are responsible for their products andapplications using TI components. To minimize the risks associated with Buyers products and applications, Buyers should provideadequate design and operating safeguards.

    TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, orother intellectual property right relating to any combination, machine, or process in which TI components or services are used. Informationpublished by TI regarding third-party products or services does not constitute a license to use such products or services or a warranty orendorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of thethird party, or a license from TI under the patents or other intellectual property of TI.

    Reproduction of significant portions of TI information in TI data books or data sheets is permissible only if reproduction is without alterationand is accompanied by all associated warranties, conditions, limitations, and notices. TI is not responsible or liable for such altereddocumentation. Information of third parties may be subject to additional restrictions.

    Resale of TI components or services with statements different from or beyond the parameters stated by TI for that component or service

    voids all express and any implied warranties for the associated TI component or service and is an unfair and deceptive business practice.TI is not responsible or liable for any such statements.

    Buyer acknowledges and agrees that it is solely responsible for compliance with all legal, regulatory and safety-related requirementsconcerning its products, and any use of TI components in its applications, notwithstanding any applications-related information or supportthat may be provided by TI. Buyer represents and agrees that it has all the necessary expertise to create and implement safeguards whichanticipate dangerous consequences of failures, monitor failures and their consequences, lessen the likelihood of failures that might causeharm and take appropriate remedial actions. Buyer will fully indemnify TI and its representatives against any damages arising out of the useof any TI components in safety-critical applications.

    In some cases, TI components may be promoted specifically to facilitate safety-related applications. With such components, TIs goal is tohelp enable customers to design and create their own end-product solutions that meet applicable functional safety standards andrequirements. Nonetheless, such components are subject to these terms.

    No TI components are authorized for use in FDA Class III (or similar life-critical medical equipment) unless authorized officers of the partieshave executed a special agreement specifically governing such use.

    Only those TI components which TI has specifically designated as military grade or enhanced plastic are designed and intended for use inmilitary/aerospace applications or environments. Buyer acknowledges and agrees that any military or aerospace use of TI componentswhich have notbeen so designated is solely at the Buyer's risk, and that Buyer is solely responsible for compliance with all legal andregulatory requirements in connection with such use.

    TI has specifically designated certain components as meeting ISO/TS16949 requirements, mainly for automotive use. In any case of use ofnon-designated products, TI will not be responsible for any failure to meet ISO/TS16949.

    Products Applications

    Audio www.ti.com/audio Automotive and Transportation www.ti.com/automotive

    Amplifiers amplifier.ti.com Communications and Telecom www.ti.com/communications

    Data Converters dataconverter.ti.com Computers and Peripherals www.ti.com/computers

    DLP Products www.dlp.com Consumer Electronics www.ti.com/consumer-apps

    DSP dsp.ti.com Energy and Lighting www.ti.com/energy

    Clocks and Timers www.ti.com/clocks Industrial www.ti.com/industrial

    Interface interface.ti.com Medical www.ti.com/medical

    Logic logic.ti.com Security www.ti.com/security

    Power Mgmt power.ti.com Space, Avionics and Defense www.ti.com/space-avionics-defenseMicrocontrollers microcontroller.ti.com Video and Imaging www.ti.com/video

    RFID www.ti-rfid.com

    OMAP Applications Processors www.ti.com/omap TI E2E Community e2e.ti.com

    Wireless Connectivity www.ti.com/wirelessconnectivity

    Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265Copyright 2013, Texas Instruments Incorporated

    http://www.ti.com/audiohttp://www.ti.com/automotivehttp://amplifier.ti.com/http://www.ti.com/communicationshttp://dataconverter.ti.com/http://www.ti.com/computershttp://www.dlp.com/http://www.ti.com/consumer-appshttp://dsp.ti.com/http://www.ti.com/energyhttp://www.ti.com/clockshttp://www.ti.com/industrialhttp://interface.ti.com/http://www.ti.com/medicalhttp://logic.ti.com/http://www.ti.com/securityhttp://power.ti.com/http://www.ti.com/space-avionics-defensehttp://microcontroller.ti.com/http://www.ti.com/videohttp://www.ti-rfid.com/http://www.ti.com/omaphttp://e2e.ti.com/http://www.ti.com/wirelessconnectivityhttp://www.ti.com/wirelessconnectivityhttp://e2e.ti.com/http://www.ti.com/omaphttp://www.ti-rfid.com/http://www.ti.com/videohttp://microcontroller.ti.com/http://www.ti.com/space-avionics-defensehttp://power.ti.com/http://www.ti.com/securityhttp://logic.ti.com/http://www.ti.com/medicalhttp://interface.ti.com/http://www.ti.com/industrialhttp://www.ti.com/clockshttp://www.ti.com/energyhttp://dsp.ti.com/http://www.ti.com/consumer-appshttp://www.dlp.com/http://www.ti.com/computershttp://dataconverter.ti.com/http://www.ti.com/communicationshttp://amplifier.ti.com/http://www.ti.com/automotivehttp://www.ti.com/audio